soil sampling for bacterial diversity study

I would like to analyze bacterial diversity in contaminated soil. I' ve seen some papers in which authors tell that the sampling should be done from 0 - 0.5 m (surface to 0.5m of depth), and my question is how to take samples, with which tool?
Thanks in advance,
T

If you really want to understand the microbial diversity - culture is not the way to go.]

Sounds like you're most interested in the soil associated with "contamination." Suggest you focus on that part.

That actually is my idea, to do the metagenomic analysis of contaminated soil. Also I would like to try culture dependent approach, hopefully to isolate single strains .

I have analyzed literature regarding that particular type of contamination, and I couldn't find any info about the contaminants concentration & soil depth & bacterial diversity correlations. So, as "gebirgsziege" has said I guess I will have to go for trial and errors.